fix: Add missing dirtyChunks variable and update rendering logic

js/physics.js

@@ -1,5 +1,12 @@
 // Physics simulation functions
-function updatePhysics() {
+function updatePhysics(timestamp) {
+    // Check if we should update physics based on the update rate
+    if (timestamp && lastPhysicsTime && timestamp - lastPhysicsTime < physicsUpdateRate) {
+        return;
+    }
+    
+    lastPhysicsTime = timestamp || 0;
+    
     // Get visible chunks
     const visibleChunks = getVisibleChunks();
     
@@ -12,6 +19,7 @@ function updatePhysics() {
         if (!isVisible) continue;
         
         const chunk = getOrCreateChunk(chunkX, chunkY);
+        let chunkModified = false;
         
         // Process from bottom to top, right to left for correct gravity simulation
         for (let y = CHUNK_SIZE - 1; y >= 0; y--) {
@@ -29,28 +37,42 @@ function updatePhysics() {
                 const worldX = chunkX * CHUNK_SIZE + x;
                 const worldY = chunkY * CHUNK_SIZE + y;
                 
-                if (type === SAND) {
-                    updateSand(worldX, worldY);
-                } else if (type === WATER) {
-                    updateWater(worldX, worldY);
-                } else if (type === DIRT) {
-                    updateDirt(worldX, worldY);
-                } else if (type === GRASS) {
-                    updateGrass(worldX, worldY);
-                } else if (type === SEED) {
-                    updateSeed(worldX, worldY);
-                } else if (type === GRASS_BLADE) {
-                    updateGrassBlade(worldX, worldY);
-                } else if (type === FLOWER) {
-                    updateFlower(worldX, worldY);
-                } else if (type === TREE_SEED) {
-                    updateTreeSeed(worldX, worldY);
-                } else if (type === FIRE) {
-                    updateFire(worldX, worldY);
-                } else if (type === LAVA) {
-                    updateLava(worldX, worldY);
+                // Use a lookup table for faster element updates
+                const updateFunctions = {
+                    [SAND]: updateSand,
+                    [WATER]: updateWater,
+                    [DIRT]: updateDirt,
+                    [GRASS]: updateGrass,
+                    [SEED]: updateSeed,
+                    [GRASS_BLADE]: updateGrassBlade,
+                    [FLOWER]: updateFlower,
+                    [TREE_SEED]: updateTreeSeed,
+                    [FIRE]: updateFire,
+                    [LAVA]: updateLava
+                };
+                
+                const updateFunction = updateFunctions[type];
+                if (updateFunction) {
+                    const wasModified = updateFunction(worldX, worldY);
+                    if (wasModified) {
+                        chunkModified = true;
+                    }
                 }
             }
         }
+        
+        // Mark chunk as dirty if it was modified
+        if (chunkModified) {
+            dirtyChunks.add(getChunkKey(chunkX, chunkY));
+        }
+    }
+    
+    // Adaptive physics rate based on FPS
+    if (fps < 30 && physicsUpdateRate < 32) {
+        // If FPS is low, update physics less frequently
+        physicsUpdateRate = Math.min(32, physicsUpdateRate + 2);
+    } else if (fps > 50 && physicsUpdateRate > 16) {
+        // If FPS is high, update physics more frequently
+        physicsUpdateRate = Math.max(16, physicsUpdateRate - 2);
     }
 }